using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Volo.Abp.Application.Services;
using Volo.Abp.DependencyInjection;
using MatrixFramework.Shared.Contracts.Monitoring;

namespace MatrixFramework.Shared.Application.Monitoring
{
    /// <summary>
    /// 指标应用服务
    /// 符合ABP vNext规范，提供可重用的指标功能
    /// </summary>
    public class MetricsAppService : ApplicationService, IMetricsAppService, ITransientDependency
    {
        private readonly ILogger<MetricsAppService> _logger;
        private readonly IOpenTelemetryService _openTelemetryService;

        public MetricsAppService(
            ILogger<MetricsAppService> logger,
            IOpenTelemetryService openTelemetryService)
        {
            _logger = logger;
            _openTelemetryService = openTelemetryService;
        }

        /// <summary>
        /// 获取系统指标摘要
        /// </summary>
        public async Task<MetricsSummaryDto> GetSummaryAsync(GetMetricsInput input)
        {
            using var operation = _openTelemetryService.StartOperation("Metrics.GetSummary");

            try
            {
                _openTelemetryService.AddEvent("metrics_summary_started");

                var endTime = DateTime.UtcNow;
                var startTime = endTime.AddHours(-input.Hours);

                var result = new MetricsSummaryDto
                {
                    StartTime = startTime,
                    EndTime = endTime,
                    Period = endTime - startTime,
                    TotalMetrics = GetTotalMetricsCount(),
                    Metrics = GetMetricsSummaryData(input)
                };

                _openTelemetryService.AddEvent("metrics_summary_completed", new Dictionary<string, object>
                {
                    ["metrics.count"] = result.TotalMetrics,
                    ["period.hours"] = input.Hours
                });

                return result;
            }
            catch (Exception ex)
            {
                _openTelemetryService.RecordException(ex);
                _logger.LogError(ex, "获取指标摘要失败");
                throw;
            }
        }

        /// <summary>
        /// 获取指标详情
        /// </summary>
        public async Task<MetricDetailsDto> GetDetailsAsync(string metricName, GetMetricDetailsInput input)
        {
            using var operation = _openTelemetryService.StartOperation("Metrics.GetDetails",
                new Dictionary<string, object>
                {
                    ["metric.name"] = metricName
                });

            try
            {
                _openTelemetryService.AddEvent("metrics_details_started", new Dictionary<string, object>
                {
                    ["metric.name"] = metricName
                });

                var result = new MetricDetailsDto
                {
                    MetricName = metricName,
                    StartTime = input.StartTime,
                    EndTime = input.EndTime,
                    DataPoints = GetMetricDataPoints(metricName, input),
                    Tags = GetMetricTags(metricName),
                    Unit = GetMetricUnit(metricName),
                    Aggregation = input.Aggregation
                };

                _openTelemetryService.AddEvent("metrics_details_completed", new Dictionary<string, object>
                {
                    ["metric.name"] = metricName,
                    ["data_points.count"] = result.DataPoints.Count
                });

                return result;
            }
            catch (Exception ex)
            {
                _openTelemetryService.RecordException(ex);
                _logger.LogError(ex, "获取指标详情失败: {MetricName}", metricName);
                throw;
            }
        }

        /// <summary>
        /// 获取性能指标
        /// </summary>
        public async Task<PerformanceMetricsDto> GetPerformanceMetricsAsync(GetPerformanceMetricsInput input)
        {
            using var operation = _openTelemetryService.StartOperation("Metrics.GetPerformanceMetrics");

            try
            {
                _openTelemetryService.AddEvent("performance_metrics_started");

                var result = new PerformanceMetricsDto
                {
                    Timestamp = DateTime.UtcNow,
                    System = GetSystemMetrics(),
                    Application = GetApplicationMetrics(),
                    CustomMetrics = GetCustomMetrics(input)
                };

                _openTelemetryService.AddEvent("performance_metrics_completed", new Dictionary<string, object>
                {
                    ["system.memory_mb"] = result.System.MemoryUsageMB,
                    ["application.uptime_seconds"] = result.Application.UptimeSeconds
                });

                return result;
            }
            catch (Exception ex)
            {
                _openTelemetryService.RecordException(ex);
                _logger.LogError(ex, "获取性能指标失败");
                throw;
            }
        }

        #region Private Methods

        private int GetTotalMetricsCount()
        {
            // 这里应该从实际的指标存储中获取
            // 暂时返回模拟数据
            return 25;
        }

        private Dictionary<string, MetricSummaryDto> GetMetricsSummaryData(GetMetricsInput input)
        {
            // 模拟数据，实际应该从指标存储中获取
            return new Dictionary<string, MetricSummaryDto>
            {
                ["http_requests_total"] = new MetricSummaryDto
                {
                    Count = 15420,
                    Average = 245.5,
                    Min = 12.0,
                    Max = 1234.0,
                    Sum = 3787110.0,
                    Unit = "requests"
                },
                ["http_request_duration_seconds"] = new MetricSummaryDto
                {
                    Count = 15420,
                    Average = 0.245,
                    Min = 0.012,
                    Max = 1.234,
                    Sum = 3787.11,
                    Unit = "seconds"
                },
                ["memory_usage_bytes"] = new MetricSummaryDto
                {
                    Count = input.Hours * 12, // 每5分钟一个数据点
                    Average = 134217728.0, // 128MB
                    Min = 67108864.0, // 64MB
                    Max = 268435456.0, // 256MB
                    Sum = 134217728.0 * input.Hours * 12,
                    Unit = "bytes"
                }
            };
        }

        private List<DataPointDto> GetMetricDataPoints(string metricName, GetMetricDetailsInput input)
        {
            var dataPoints = new List<DataPointDto>();
            var duration = input.EndTime - input.StartTime;
            var interval = TimeSpan.FromMinutes(5); // 5分钟间隔

            for (var time = input.StartTime; time <= input.EndTime; time += interval)
            {
                dataPoints.Add(new DataPointDto
                {
                    Timestamp = time,
                    Value = GenerateMockMetricValue(metricName, time)
                });
            }

            return dataPoints;
        }

        private Dictionary<string, string> GetMetricTags(string metricName)
        {
            return metricName switch
            {
                "http_requests_total" => new Dictionary<string, string>
                {
                    ["endpoint"] = "/api/*",
                    ["method"] = "GET,POST,PUT,DELETE",
                    ["status"] = "200,400,500"
                },
                "http_request_duration_seconds" => new Dictionary<string, string>
                {
                    ["endpoint"] = "/api/*",
                    ["method"] = "GET,POST,PUT,DELETE"
                },
                "memory_usage_bytes" => new Dictionary<string, string>
                {
                    ["process"] = "tenant-management",
                    ["type"] = "working_set"
                },
                _ => new Dictionary<string, string>()
            };
        }

        private string GetMetricUnit(string metricName)
        {
            return metricName switch
            {
                var name when name.Contains("bytes") => "bytes",
                var name when name.Contains("seconds") => "seconds",
                var name when name.Contains("requests") => "requests",
                var name when name.Contains("percent") => "percent",
                _ => "count"
            };
        }

        private double GenerateMockMetricValue(string metricName, DateTime time)
        {
            var random = new Random((int)time.Ticks);

            return metricName switch
            {
                "http_requests_total" => random.Next(100, 500),
                "http_request_duration_seconds" => random.NextDouble() * 2.0,
                "memory_usage_bytes" => 134217728 + (random.NextDouble() - 0.5) * 67108864, // 128MB ± 32MB
                _ => random.NextDouble() * 100
            };
        }

        private SystemMetricsDto GetSystemMetrics()
        {
            var process = Process.GetCurrentProcess();

            return new SystemMetricsDto
            {
                MemoryUsageBytes = GC.GetTotalMemory(false),
                ProcessorCount = Environment.ProcessorCount,
                WorkingSetBytes = process.WorkingSet64,
                OsVersion = Environment.OSVersion.ToString(),
                MachineName = Environment.MachineName
            };
        }

        private ApplicationMetricsDto GetApplicationMetrics()
        {
            var process = Process.GetCurrentProcess();

            return new ApplicationMetricsDto
            {
                UptimeSeconds = (DateTime.UtcNow - process.StartTime).TotalSeconds,
                ProcessId = process.Id,
                ThreadCount = process.Threads.Count,
                RequestCount = 15420, // 模拟数据
                AverageResponseTimeMs = 245.5, // 模拟数据
                ErrorRate = 0.02 // 模拟数据
            };
        }

        private List<CustomMetricDto> GetCustomMetrics(GetPerformanceMetricsInput input)
        {
            var metrics = new List<CustomMetricDto>();

            if (input.IncludeSystemMetrics)
            {
                metrics.Add(new CustomMetricDto
                {
                    Name = "tenant_count",
                    Value = 150,
                    Unit = "tenants",
                    Tags = new Dictionary<string, string> { ["type"] = "active" }
                });

                metrics.Add(new CustomMetricDto
                {
                    Name = "cache_hit_ratio",
                    Value = 0.85,
                    Unit = "ratio",
                    Tags = new Dictionary<string, string> { ["cache_type"] = "redis" }
                });
            }

            if (input.IncludeApplicationMetrics)
            {
                metrics.Add(new CustomMetricDto
                {
                    Name = "database_connection_pool",
                    Value = 12,
                    Unit = "connections",
                    Tags = new Dictionary<string, string> { ["status"] = "active" }
                });
            }

            return metrics;
        }

        #endregion
    }
}